Chest drains are often used in connection with cardiac and thoracic surgical procedures in order to remove fluids from the chest cavity of a patient. Suction is typically used to draw fluid into the chest drain. Various devices have been proposed for chest drainage over the years, including for example those disclosed in U.S. Pat. No. 4,988,342; U.S. Pat. No. Re. 35,225; U.S. Pat. Nos. 5,401,262; 5,807,358; 6,210,383; and 6,358,218, each of which is incorporated by reference herein.
Such devices may operate within a relatively small magnitude of suction and may include a suction regulator mechanism. For example, in some such devices, operation may occur in a range of −10 to −40 cm H2O. Because they often apply suction directly to a patient's chest cavity, chest drainage devices ideally provide a low and consistent suction level that is compatible with human physiology.
Accordingly, it is desirable for chest drainage devices to include a suction monitor so that a medical professional can monitor the suction potential applied to the chest drainage device. For example, U.S. Pat. No. 5,807,358 discloses a passively-operated bellows in the form of a pleated polymer tube which has one end closed and another end opened and sealably affixed to an opening in a side wall of the chest drainage device. The outside of the bellows experiences the prevailing suction, and the bellows extends along a substantially horizontal line behind a face plate of the chest drainage device with its extension increasing as a greater degree of suction is applied. An elbow-shaped clear space can be provided in the face plate of the chest drainage device to improve the readability of the bellows.
It may also be desirable in chest drainage devices to monitor the level of suction that may be prevailing in the chamber in which fluids are collected from a patient's chest cavity. For example, as disclosed in U.S. Pat. No. 5,807,358, a float ball may be provided to ride up and down in a narrow column of water to indicate the level of excess suction prevailing in the collection chamber. If in the event that suction in the collection chamber exceeds the level of suction desired, the water level in the column rises and the position of the float ball thus warns the user of excessive negativity.
U.S. Pat. Nos. 4,715,855 and 4,889,531 disclose a fluid drainage system including a suction chamber and a fluid collection chamber. The system further includes diaphragm assemblies wherein flexing of a diaphragm operates a pressure measuring means. Specifically, a patient negativity diaphragm extends over an opening in a wall of a chamber, a push rod is attached to a diaphragm, and a dial is mounted on a pivot movable by the push rod for cooperating with a scale. When the atmospheric pressure outside of the chamber exceeds that in the chamber, the diaphragm flexes inwardly, rotating the dial to indicate the extent of patient negativity.
Also, the '855 and '531 patents disclose a gauge, provided to measure pressure in a suction chamber, that includes a diaphragm which covers an opening in a wall between an upper chamber (at atmospheric pressure) and the gauge (located in the suction chamber). The diaphragm flexes according to the pressure differential between the pressure in the chamber and atmospheric pressure, and such flexure is reflected in linear movement of a push rod, which in turn pivots a dial to reflect negative pressure on a scale.
U.S. Pat. No. 4,747,843 discloses a system pressure indicator connected to a chamber of a thoracic drainage device. The indicator provides, via sign means, a visual indication of whether the pressure in the collection container is negative or positive. A tubular elastomeric membrane is closed at its distal end and sealed by an O-ring at its proximal end. The sign means bears the letters “YES” to indicate negative pressure, and a magnifying lens is mounted in a cover panel so that the elastomeric membrane is visible through the lens. An aperture in the cover panel permits atmospheric air to enter the recess within which the indicator is positioned. When gases within the collection chamber are at negative pressure, the to elastomeric membrane collapses due to the higher atmospheric pressure on the outside of the membrane. In the collapsed state, the sign bearing the term “YES” is visible through the membrane, which indicates to the attending medical personnel that the collection container is under negative pressure. If the pressure in the collection container is positive, the membrane will expand and the word “YES” will not be visible, which indicates to the attending medical personnel that the pressure in the collection container is positive.
A visual indication of the level of applied suction is provided in the '843 patent by a transparent suction indicator flow tube and a flow ball. An aperture in the bottom of the flow tube allows atmospheric air to enter the bottom of the tube and the difference in pressure between the gas in a chamber and atmospheric pressure causes the ball to rise in the tube an amount proportional to the pressure difference, which may be indicated by a calibrated scale on the flow tube. The flow tube is positioned adjacent a front wall of the device for visualization.
Nevertheless, improvements to such chest drainage devices are continuously sought in order to improve performance, reduce cost, or improve the ease with which the devices are used by medical professionals.